PHILADELPHIA (CBS) – Signs have been cropping up in North Philadelphia that advertise, “Cash for diabetic test strips.” They’re part of a growing “gray market” in an expensive medical supply.

The strips, which measure blood glucose levels, can cost as much as a dollar apiece but insurance reduces that amount. The “cash for strips” business buys extra strips at that reduced rate and resells them for a profit.

Doctors often counsel diabetic patients to test several times a day, but diabetes educator Nadine Uplinger says many people don’t like to test and the incentive of cash endangers their health, “We want people to test, but they don’t have a lot of resources and if they don’t want to bother testing and they can get money for it, I’m sure they’re doing it.”

Uplinger was outraged when the signs appeared outside Einstein’s clinic in North Philadelphia. The practice is legal, unless the strips are purchased through Medicare and Medicaid, but Uplinger finds it unethical, “They’re targeting North Philly, which is underserved to begin with, and it was upsetting to myself and my colleagues to see that they’re targeting this population when we’re trying so desperately to get people to test their blood sugar so that they can better self-manage their disease.”